Muffler



May 24, 1938.

P. G. PEIK MUFFLER Filed sept. 17, i954 4 Sheets-Sheet l Ail! - mvENToR.paaf'pz' Y Q@ y agi ATTORNY? Patented May v274, 193g UNITED STATESMUFFLER Paul G. Peik,

Cleveland, Ohio Application September 17, 1934, Serial No. 744,380

16 Claims.

This invention relates, as indicated, to mufflers, and moreparticularly, to muillers for sllencing the exhaust of internalcombustion engines, particularly automotive engines.

It is one of the objects of my invention to provide a muiiler whichcombines a high degree of silencing eiciency with extreme compactness,yet has low back pressure and is relatively simple and cheap tomanufacture.

It is a further object of my invention to provide a muffler of thecharacter described in which the gas stream in passing therethrough is,for a major portion of the extent of such travel, in contact with theouter closure shell of the mufer so that the temperature of the exhaustgases may be appreciably reduced during the passage thereof through themuiller with the advantages hereinafter more fully explained.

It is a further object of my invention to pro- 20 vide a mufller of thecharacter described in which there is provided an unbaffled passage forthe gas through the mulller, which passage is so arranged that a minimumof back pressure is generated, so that it is in contact with the outerclosure shell of the muffler, as above explained, and further, so thatit is bordered by sound attenuating chambers throughout the majorportion of its travel through the mul'ller.

Other objects of my invention will appear as the description proceeds.To the accomplishment of the foregoing and related ends, said invention,then, consists of the means hereinafter fully described and particularlypointed out in the claims.

The annexed drawings and the following description set forth in detailcertain mechanism embodying the invention, such disclosed meansconstituting, however, but several of the various mechanical forms inwhich the principle of the invention may be used.

In said annexed drawings:-

Fig. 1 is a somewhat diagrammatic representation of the construction ofone form of muffler according to my invention; Fig. 2 is an endelevational view of the structure illustrated in Fig. 1; Fig. 3 is atransverse sectional view of the structure illustrated in Fig. 1 takenon a plane substantially indicated by the line 3 3; Fig. 4 is afragmentary elevational view of one of the elements of the constructionillustrated in the previous figures showing the arrangement of thelouvcrs therein; Fig. 5 is a transverse sectional view similar to Fig. 3showing, however, a slight modification in the arrangement of theseveral parts forming the structure illustrated in Fig. 1; Fig. 6 is asomewhat diagrammatic representation of a slightly different form ofmuiller construction embodying the principles of my invention; Fig. '7is a longitudinal, transverse, sectional view of the structureillustrated in Fig. 6 taken on a plane substantially indicated by theline 1 1; Fig. 8 is a somewhat diagrammatic representation of yetanother form of muffler embodying the principles of my invention; Figs.9 and 10 are, respectively, transverse sectional views of the structureillustrated in Fig. 8 taken on a plane substantially indicated by thelines 9-9 and IO-l; Figs. 11, 12, 13 and 14 are views showing details ofconstruction of the assembly illustrated in Figs. 8 to l0; Figs. 15 and16 are respectively transverse sectional and end elevational views ofanother form of muiller constructed in accordance with the principles ofmy invention, Fig. 15 being a sectional view taken on a planesubstantially indicated by the line l5-l5 in Fig. 16; Fig. 17 is a Viewsimilar to Fig. l5 but showing a further modied form of construction;and Fig. 18 is an end elevational view of the structure disclosed inFig. 1'7.

Referring now more specifically to the drawings and more especially toFigs. 1 to 3, the muliler herein illustrated comprises a substantiallyrectangular body generally indicated at l, which is formed by means ofsubstantially iiat side members 2 and 3 between which are disposed andsecured two substantially identical looped strips 4 and 5 formed of flatstock and arranged in substantially parallel relation to each other. Attheir terminals 6 and l the strips 4 and 5 are brought together so as toprovide substantially elliptical extensions 8 and 9 to which exhaustconduits may be secured. Closure members l0 and Il are employed to closethe spaces between the extensions 8 and 9 and the rebent strips 4 and 5so that a closed shell is provided.

Extending between the side walls 2 and 3 in the spaces within the casingl defined between rebent strips 4 and 5, are a plurality of partitionsrespectively indicated by the ordinals I2 to 20 and l2 to 20. Thesepartitions dene a plurality of sound attenuating chambers respectivelydesignated by the ordinals 2| to 30 and 2| to The strips 4 and 5 areprovided with louvers. as indicated in Fig. 1, and the partition membersl2 et seq. are likewise provided with louvers, whereby sound waves fromthe stream of gas passing through the muliler may pass into the varioussound attenuating chambers.

As above indicated the members 4 and 5 may be respectively formed fromidentical fiat strips coiled to the contour illustrated in Fig. l andpositioned between the side members 2 and 3 as the muffler is`assembled. In order to facilitate assembly the side plates 2 and 3 maybe provided with struck out portions conforming to the configuration tobe taken by the members 4 and 5 so that as the side members 2 and 3 arebrought together, the members d and 5 will be automatically located andsecured in the desired position. Attention is also directed to the factthat the partition members numbered l2 to 20 may be formed of accordionfolded iiat stock, which, along its longitudinal edges is provided withlateral flanges by which the partition members may be secured to theside plates 2 and 3. At this point, it should also be noted that theaccordion folded strip forming the partition members l2 to 29 isidentical with the similarly formed strip which provides the partitionsl2' to 2U'. In order to facilitate assembly of the two accordion foldedstrips providing the intermediate partitions, the side plates 2 and 3may be provided with triangular shaped indentations arranged to conformto the desired location of the accordion folded strips so that theintermediate partition members are held in proper position during anduntil they are secured to the side walls` as by welding.

As most clearly illustrated in Fig. 3, the strips 4 and 5 aresubstantially fiat and arranged normal to the plates 2 and 3 to whichthey are secured in spaced relation along their longitudinal edges. Itmay be desirable to transversely dish the strips Il and 5 in the mannerillustrated in Fig. 5, wherein ordinals bearing the subscript al havebeen employed to designate parts similar to those shown in Fig. 3. InFig. 5 the strips 4a and 5a are, in their areas which form a part of theouter shell, dished sufficiently so that they may have theirlongitudinal edges brought into abutting relation and joined to the sidemembers 2a and 3a in one line instead of two spaced lines as indicatedin Fig. 3.

From the above description, it is believed that the action of themuilier in silencing the exhaust of internal combustion engines will beapparent to anyone versed in the art. However, the following briefexplanation is offered of the function of the muiiler described toaccomplish this end.

While the main body of the gas flows. around the S-shaped passage and isacted upon by the sound wave attenuating functions of the adjacentchambers, a portion of the gas short circuits from the incoming passagethrough the reverse passage direct into the outgoing passage by virtueof the openings in the partition l2 et seq. and I2' et seq. Restrictedcommunication is thus afforded between Various parts of the main gasstream in which the sound waves are out of phase with resultant increasein sound attenuation, as well as reduction in back pressure. In thisparticular modification of the invention it has been found that agreater volume of gas can be permitted to thus short circuit withoutsuffering undue arn- `plitude in the sound waves, which likewise crossover, due to the relative position of the sound attenuating chamberswith respect to each other and the gas stream. For example, the soundwaves short circuiting from any one chamber facing the incoming streamare distributed or spread out into the two adjacent chambers facing thereverse stream and after being acted upon by the out of phase soundwaves in the reverse passage over an area equal to the face of these twochambers, cross over and in the same manner are spread out further bythe time they enter the outgoing passage. In this connection it shouldbe borne in mind that the energy potential across. a wave front after ithas left its source is inversely proportional to the area or spread ofthe wave front; also that both the back pressure and amplitude of thesound waves are decidedly greater at the incoming end of the muiler thanat the outgoing.

There is a very substantial cooling effect secured due to the fact thatthe main gas stream is in direct contact with the outer shell of themuliier during the major portion of its passage therethrough withresultant beneficial effect up on back pressure and sound waveattenuation.

The substantially flat or rectangular stream employed can be reversed,as shown, in a very short radius without any appreciable increase inback pressure.

The construction illustrated in Figs. 6 and l is based upon the samefundamental principles underlying the construction of the mufflerillustrated in Fig. 1. The muffler illustrated in Figs. 6 and 7comprises a substantially rectangular body generally indicated at 3lformed by means of two substantially fiat side plates 32 and 33,intermediately of which there are positioned two coiled flat platesgenerally indicated at 34 and 35. The latter plate is so formed andsecured to the side plates 32 and 33 as to form a completely closedchamber within which the plate 34, perforated throughout the majorportion of its length, is in spaced relation to the plate 35.

Mounted within the casing 3l and separating the inner space dened by thecoiled plate 34 and the side plates 3l and 32 into a plurality of soundattenuating chambers, are partitions respectively indicated by 3B to 4l,both inclusive.

Another strip i8 coiled into oblong form and positioned between the sideplates and partition members, as shown in Fig. 6, provides a centralchamber making possible restricted communication between the Varioussound attenuating chambers in which the said waves are out of phase,resulting in a reduction in back pressure and an increase in thesilencing effect of the muler.

As most clearly illustrated in Fig. 7, the side plate 33 is providedwith an opening, into which there extends a conduit generally indicatedat 49 for the incoming gases. It will be noted that the conduit i9extends through partition 3l and terminates in an opening providedtherefor in partition 38. The strips 34 and 35 are at one end broughttogether and formed into a substantially tubular extension 52 to whichthe usual outgoing pipe is secured.

The modiiication illustrated in Figs. 8 to 14 comprises a substantiallycylindrical shell, generally indicated at 55, to which there is secured,at its opposite ends, headers 5&3 and 5l respectively, provided withinlet and outlet orifices 58 and 59. The space defined by the shell 56is divided into a plurality of sections, generally indicated at 60, BIand 62. Each of these sections includes a substantially cylindricalinner shell 63, 64 and 65, respectively. These inner shells positionedbetween transversely extending partition members BG, 61, 68 and 69 areprovided with louvers, as most clearly illustrated in Fig. 9. Thelouvers may, in certain sections, such as 63 and 64, be faced towardsthe gas stream and in certain other sections such as 66 faced away fromthe gas stream; or the louvers in certain portions of each section maybe faced towards the gas stream and in other portions of the samesections faced away from or trailing the gas stream. 'I'he spacesdefined by the inner shells 63, 64 and 65 are divided into a pluralityof sound attenuating chambers by means of radially extending partitionmembers such as 18, 12, 13 and 14. In order to facilitate themanufacture, the partition members 12 and 14 may be made from one piecebent angularly in the manner illustrated in Fig, 11. At this point, itmight be well to note that the opposite radially extending edges of theelement 10 are respectively denoted by the ordinals 1I and 1Ia. Theangularly bent section illustrated in Fig. 1l is at the line of suchbend provided with a slot as indicated at 15, so that the partitionmembers 10 and 13, likewise formed of one piece and bent angularly inthe manner illustrated in Fig. 13, may be conveniently assembledtherewith in the manner illustrated in said last-named figure; suchassembly is made possible by the provision of a slot in the plateforming the members 10 and 13 and arranged at the line of juncture ofsuch elements.

As previously indicated the elements 12, 13 and 14 extend axially andradially of the inner shell in flat planes. 'I'he elements 10 are,however, twisted into substantially helical shape and extend through theinner shells 63, 64 and 65 into engagement with the outer shell. Theseelements 10, therefore, provide helically arranged streamlined turnsbetween the inner and outer shells whereby the gas progressing from oneend of a muffler to another in the space defined by the inner and outershells flows in a circumferential path for a major portion of its travelthrough each section and then moves helically into the next section.

The inner shell in the area 11 at the gas-receiving end of the muffleris bent inwardly on the left-hand side of the member 10, so that the gasentering the section 60 through the opening 18 in the partition member66 may have an unrestricted and unobstructed path into and through saidsection.

Since the width of the gas passage between adjacent members 18 on theline indicated at X is less than the axial distance between partitions66, 61, etc., the inner shell in these areas may likewise be depressedinwardly as indicated at 19 in order to compensate for this reduction inwidth of the gas stream. The inner shell 65 at may likewise be depressedinwardly as at 11 in Fig. 9 in order to afford an unobstructed passagefor the gas through the outlet orifice 8l in the partition member 69.The partition members 66, 61, et seq. may, as most clearly illustratedin Fig. 10, be provided with spaced groups of louvers indicatedgenerally at 82, which louvers are so arranged as to be positionedbetween the sound attenuating chambers of adjacent sections of themuflier. These louvers are designed primarily to reduce the backpressure of the muffier and also to assist in the sound attenuatingfunction of the central chambers of the muflier.

In assembling the muffler as illustrated in Fig. 8, it may beexpeditious to build up as separate units each of the sections 63, 64and G5 with their internal partition members 10 etc. After theseseparate units have been thus individually ccnstructed, they may then benested and assembled within the main outer shell 55. In order tofacilitate this nesting and assembly of the muffler sections, eachsection is assembled complete to one of the partition members such as 61to which the various parts are secured as by welding, as shown mostclearly in Fig. 9. It will be apparent that if the various parts of theinner structure are assembled on the raised portions of the partitionmembers as illustrated at 64a in Fig. 14, after such assembly is inplace it will present a dished in area into which the open end of thenext adjacent section may nest and be held in place. At this point itmay be noted that the partition members 10, 12, 13 and 14 are preferablyprovided with securing and supporting flanges along their edges, asindicated in Fig. 9.

The modification illustrated in Figs. 15 and 16 is fundamentally similarto the construction illustrated in Fig. 1. Instead, however, ofproviding the gas passage through the muffler by means of two looped orrebent plates such as 4 and 5 which are, as illustrated in Fig. 1,perforated in certain areas to provide sound attenuating chambersbetween the partition members disposed intermediately of such plates, Imay prefer to construct the muffler from two principal plates such as 81and 88 which, of course, are disposed between side plates 89 and 90. Theplate 81 is maintained substantially straight until it reaches thepoint, generally indicated at 9 I, where it is curved through thesections denoted by 92 and thence continues straight again until itreaches the area within the upper righthand portion of the muffler whereit is bent to the form shown so as to provide a plurality of oppositelydirected sound attenuating chambers between the side walls of the outershell.

In a similar fashion, the plate 88 is formed to provide the top closurefor the muffler and at its lower end to provide a plurality ofoppositely directed sound attenuating chambers in the lower and lefthandside of the muffler, as viewed in Fig. 15. The plates 81 and 88, attheir ends, have auxiliary plates 93 and 94 associated therewith, whichlast-named plates are so formed as to cooperate with the formed ends ofthe plates 81 and 88 to respectively provide substantially ellipticalextensions 95 and 96 to which inlet and outlet conduits may berespectively connected.

It will be understood, of course, that the rebent portions of the strips81 and 88 which provide the sound attenuating chambers may be provided,along their opposite edges, with laterally extending fianges (notshown), which will facilitate the securing of these portions of thestrips to the side plates 89 and 90 and thus generally facilitateassembly.

The strips B1 and 88 are provided with openings or louvers through whichlimited cross flow between the several gas streams may take place. Theseopenings or louvers may be formed in the strips before the same are bentinto shape and if formed in the lines along which it is desired to bendthe strips, the forming of such strips will be greatly facilitated.

The construction illustrated in Figs. 15 and 16 provides a continuousunbafiied passage for the gas through the muffler in the directionsdenoted by the arrows, which stream of gas is bordered on one sidethroughout the major portion of its travel through the muffler by theouter shell and on its other side by a plurality of sound attenuatingchambers. It is believed that in the light of the previous descriptionof the muffler illustrated in Fig. l, the construction and operation ofthe muffler illustrated in Figs. 15 and 16 may be understood without afurther detailed description.

In connection with the description of Fig. 5, it will be noted that theouter portions of the strips il. and 5 have been indicated as dished. Itis to be understood that this same modiiication may be applied to allother forms and that such eX- pedient is present in the modificationillustrated in Figs. 15 and 16.

In the foregoing description the openings whereby communication isaiiorded between the gas stream and the sound attenuating chambers andbetween the several sound attenuating chambers have been referred to aslouvers. It is to be understood, however, that such openings may bemerely plain openings and not louvers as disclosed and provided withadjacent lips.

In the foregoing description it will be noted several parts, such asstrips 4 and 5, have been shown in certain respects continuous and incertain respects discontinuous. It is to be understood, of course, thatthe principles of my invention are applicable to all forms ofconstructions regardless of the particular manner in which the muiileris fabricated. In other words, where the several elements have beenshown as continuous, they may be made discontinuous from differentstrips and where they have been shown discontinuous, they may, ifdesired and expedient, be made continuous.

The modification illustrated in Fig. 17 is chal'- acterized by the factthat the inlet opening 97 for the gas is arranged centrally of one endof the muiiier, as most clearly illustrated in Fig. 18. The gas enteringthe muiiler through the conduit S8 passes across a gap 99 beforeentering the central passage ill. The chamber Il serves as a means fordampening out pressure impulsesy due to the opening of diiierent exhaustvalves in the engine and such impulses are further ironed out due to thefact that the central passage l is in communication with soundattenuating chambers on both sides thereof. The construction of themuiiier illustrated in Figs. 17 and 18 has a further advantage in thatthe permissible cross-oven of gas from the incoming central stream tothe other streams in the muiler is substantially greater than thepermissible cross-over of gas flow in constructions such as illustratedin` the previous iigures. In all principal respects, the constructionillustrated in these last-named iigures is fundamentally the same asthat illustrated in the previous figures, so that a further descriptionof its construction and function is believed unnecessary.

It may be desired to ll the spaces between the main gas passages in theseveral illustrated forms of my invention with some material such assteel wool or the like, thus combining in one structure the advantagesof an absorption-type muffler with my reverse stream muier. When suchmaterial is employed, it is obvious that the partition members such asl2, 3S, 'I4 etc. may be omitted.

Other modes of applying the principle of my invention may be employedinstead of the one explained, change being made as regards the mechanismherein disclosed, provided the means stated by any of the followingclaims or the equivalent of such stated means be employed.

I therefore particularly point out and distinctly claim as my invention:

l. An exhaust silencer for internal combustion engines and the likecomprising a casing including an outer closure shell and innerpartitions, at least some of which partitions are perforated, saidpartitions so arranged relatively to each other and to said shell as toprovide a circuitous passage unobstructed throughout its length for theexhaust gases through said casing, portions of said passage beingoppositely extending, said passage throughout the major portion of itsextent bordered on one side by said closure shell and on another side bya perforated partition defining a sound attenuating chamber lyingbetween oppositely extending portions of said passage.

2, An exhaust silencer for internal combustion engines and the likecomprising a casing including an outer closure shell and innerpartitions dividing a portion of the space enclosed by said shell into aplurality of sound attenuating chambers, said partitions so arrangedrelatively to each other and said shell as to provide a circuitouspassage unobstructed throughout its length through said casing, portionsof said passage being oppositely extending with the major extent of suchpassage bordered on one side by said closure shell and on another sideby a partition having openings into sound attenuating chambers lyingbetween oppositely extending portions of said passage.

3. An exhaust silencer for internal combustion engines and the likecomprising a casing including an outer closure shell and innerperforated partitions dividing a portion of the space enclosed by saidshell into a plurality of sound attenuating chambers, said partitions soarranged relatively to each other and said shell as to provide acircuitous passage of substantially uniform cross-sectional area throughsaid casing, portions of said passage being oppositely extending, and

said passage throughout the major portion of its extent bordered on oneside by said closure shell and on another side by a partition havingopenings into said sound attenuating chambers lying between oppositelyextending portions of said passage.

4. An exhaust silencer for internal combustion engines and the likecomprising a casing including an outer closure shell and innerpartitions dividing a portion of the space enclosed by said shell into aplurality of sound attenuating chambers, said partitions so arrangedrelatively to each other and said shell as to provide a continuouscircuitous passage unobstructed throughout its length for the exhaustgases through said casing, portions of said passage being oppositelyextending, said passage throughout the major portion of its extentbordered on at least one side by a partition having openings intodifferent successively arranged sound attenuating chambers lying betweenoppositely extending portions of said passage.

5. An exhaust silencer for internal combustion engines and the likecomprising a casing including an outer closure shell and innerpartitions dividing a portion of the space enclosed by said shell into aplurality of sound attenuating chambers, said partitions so arrangedrelatively to each other and said shell as toprovide a cir-- cuitouspassage unobstructed throughout its length for the exhaust gases throughsaid casing, portions of said passage being cppositely extending, saidpassage throughout the major portion of its extent bordered on one sideby said closure shell and on another side by a partition having openingsinto different successively arranged sound attenuating chambers lyingbetween oppositely extending portions of said passage.

6, An exhaust silencer for internal combustion engines and the likecomprising a casing includ- Cil ing an outer closure shell and innerpartitions dividing a portion of the space enclosed by said shell into aplurality of sound attenuating chambers, said partitions so arrangedrelatively to each other and said shell as to provide a continuous`circuitous passage unobstructed throughout its length for the exhaustgases through said casing, portions of said passage being oppositelyextending, said passage throughout the major portion of its extentbordered on at least one side by a partition having openings intodifferent successively arranged sound attenuating chambers and most ofsuch successive chambers being sequentially different in size lyingbetween oppositely extending portions of said passage.

7. An exhaust silencer for internal combustion engines and the likecomprising a casing including an outer closure shell and innerpartitions dividing a portion of the space enclosed by said shell into aplurality of sound attenuating chambers, said partitions so arrangedrelatively to each other and said shell as to provide a circuitouspassage unobstructed throughout its length for the exhaust gases throughsaid casing, portions of said passage being oppositely extending, saidpassage throughout the major portion of its extent bordered on one sideby said closure shell and on another side by a partition having openingsinto different successively arranged sound attenuating chambers and mostof such successive chambers being sequentially different in size lyingbetween oppositely extending portions of said passage.

8. An exhaust silencer for internal combustion engines and the likecomprising a casing including an outer closure shell and inner partitionmembers dividing a portion of the space enclosed by said shell into aplurality of sound attenuating chambers, said partitions so arrangedrelatively to each other and said shell as to provide a substantiallyS-shaped passage for the exhaust gases through said casing, said passagebordered on one side throughout the major portion of its extent by apartition having openings into said attenuating chambers.

9. An exhaust silencer for internal combustion engines and the likecomprising a casing including an outer closure shell and inner partitionmembers dividing a portion of the space enclosed by said shell into aplurality of sound attenuating chambers, said partitions so arrangedrelatively to each other and said shell as to provide a substantiallyS-shaped passage for the exhaust gases through said casing, said passagebordered on one side throughout the major portion of its extent by saidshell.

10. An exhaust silencer for internal combustion engines and the likecomprising a casing including an outer closure shell and inner partitionmembers dividing a portion of the space enclosed by said shell into aplurality of sound attenuating chambers, said partitions so arrangedrelatively to each other and said shell as to provide a substantiallyS-shaped passage for the exhaust gases through said casing, said passagebordered on one side throughout the major portion of its extent by saidshell and on another side by said sound attenuating chambers.

11. An exhaust silencer for internal combustion engines and the likecomprising a substantially rectangular casing having ilat sides,reversely bent substantially flat strips arranged in substantiallyparallel relation with respect to each other and normal to said sideswhereby a substantially closed chamber is formed provided with anS-shaped continuous unobstructed passage therethrough for the exhaustgases.

12. An exhaust silencer for internal combustion engines comprising acasing including an outer closure shell and inner partition membersdividing a portion of the space enclosed by said shell into a pluralityof sound attenuating chambers, said partitions and closure shell soarranged as to provide a substantially S-shaped passage for gas flowthrough the silencer, such passage reversing the direction of gas flowin clockwise and counter-clockwise directions.

13. An exhaust silencer for internal combustion engines and the likecomprising a substantially rectangular casing, a plurality of partitionsin said casing defining a circuitous passage unobstructed throughout itslength for the exhaust gases through said casing, said passagethroughout the major portion of its extent being substantiallyrectangular in cross-section with reversals in direction thereof onsmooth curves, and certain of said partitions perforated to permit crossflow between streams of .gas flowing in opposite directions.

14. An exhaust silencer for internal combustion engines and the like,comprising a substantially rectangular casing, a plurality of partitionsin said casing defining a passage for the exhaust gases through saidcasing, said passage unobstructed throughout its length, substantiallyrectangular in cross-section for the major portion of its extent andreversing a plurality of times by means of smooth curves, and certain ofsaid partitions perforated so as to permit limited cross flow betweenstreams of gas ilowing in opposite directions.

15. An exhaust silencer for internal combustion engines and the likecomprising two substantially parallel sheet members and partitionsnormally placed therebetween, forming therewith a continuous passage ofsubstantially uniform rectangular cross-section turned and returned uponitself to approximate an S-form, and forming a plurality of chamberspositioned laterally of said passage between the turns thereof, andapertures through the walls of said passage whereby compressed gasespassing through said passage expand into said chambers.

16. An exhaust silencer for internal combustion engines and the likecomprising two substantially parallel sheet members and partitionsnormally placed therebetween, forming therewith a continuous passage ofsubstantially uniform rectangular cross-section turned and returned uponitself to approximate an S-form, and forming a plurality of chamberspositioned laterally of said passage between the turns thereof, andapertures through the walls of said passage whereby compressed gasespassing through said passage expand into said chambers, and passtherethrough.

PAUL G. PEIK.

